The history of Yoga was divided into four periods: the Vedic Period, Pre-Classical Period, the Classical Period, and Post-Classical Period.
The existence of the "Veda" marks this period. The Veda is the sacred scripture of Brahmanism that is the basis of modern-day Hinduism. It is a collection of hymns that praise divine power. The Vedas contain the oldest known Yogic teachings and the teachings found in the Veda is called Vedic Yoga. These techniques are rituals and ceremonies that strive to surpass the limitations of the mind. During this time, the Vedic people relied on Rishi's (saint) or dedicated Vedic Yogi's to teach them how to live in divine harmony. Rishi's or Yogi's lived in seclusion (in forests) and were gifted with the ability to see the ultimate reality through their intensive spiritual practice.
The 200 scriptures of the Upanishads (the conclusion of the revealed literature) were created in this period that describe the inner vision of reality resulting from devotion to Brahman. The Upanishads further explain the teachings of the Veda's and the three subjects: the ultimate reality (Brahman), the transcendental self (atman), and the relationship between the two. Yoga shares some characteristics not only with Hinduism but also with Buddhism that we can trace in its history. During the sixth century B.C., Buddha started teaching Buddhism, which stresses the importance of Meditation and the practice of physical postures. Siddhartha Gautama, the first Buddhist to study Yoga, achieved enlightenment at the age of 35.
Later, around 500 B.C., the Bhagavad-Gita or Lord's (Krishna) Song was created and this is currently the oldest known Yoga scripture. The Gita was a conversation between Prince Arjuna and God-man Krishna and it stresses the importance of opposing evil. It is devoted entirely to Yoga and has confirmed that it has been an old practice for some time. However, it doesn't point to a specific time wherein Yoga could have started. The central point of the Bhagavad Gita is "to be alive means to be active and to avoid ego avoid difficulties in life". Just as the Upanishads further the Vedas, the Gita builds on and incorporates the doctrines found in the Upanishads. In the Gita, three facets must be brought together in our lifestyle: Bhakti, or loving devotion, Jnana; knowledge, or contemplation, and Karma, selfless actions. The Gita then tried to unify Bhakti Yoga, Jnana Yoga, and Karma Yoga and it is because of this that it has gained importance.
The Classical Period is marked by another creation - the Yoga Sutra. Written by Patanjali around the second century, it was an attempt to define and standardize Classical Yoga. It is composed of 195 aphorisms or sutras (Sanskrit word which means thread) that expound upon the Raja Yoga and its underlying principle; Patanjali’s Eightfold Path also called Eight Limbs of Yoga. The eight limbs are Yama, which means social restraints or ethical values, Niyama’s, which is the personal observance of purity, tolerance, and study, Asanas, the effortless pose, Pranayama, breath regulation/control, Pratyahara, withdrawal of sense in preparation for Meditation, Dharana, concentration, Dhyana, Meditation and Samadhi, ecstasy.
Patanjali believed that each individual is a composite of matter (Prakriti) and spirit (purusha). He further believed that the two must be separated to cleanse the spirit - a stark contrast to Vedic and Pre-Classical Yoga which signify the union of body and spirit. Patanjali's concept was dominant for some centuries some Yogis focused exclusively on Meditation and neglected the Asana (Yoga poses). It was only later that the belief in the body as a temple was rekindled and attention to the importance of the Asana was revived. This time, Yogis attempted to use Yoga techniques to change the body and make it eternal.
At this point, we see a proliferation of literature as well as the practice of Yoga. Post-classical Yoga differs from the first three since it focuses more on the present. It no longer strives to liberate a person from reality but teaches one to accept it and live in the moment. Yoga was introduced in the West during the early 19th century. It was first studied as part of Eastern Philosophy and began as a movement for health and vegetarianism around the 1930s. By the 1960s, there was an influx of Indian teachers who expounded on Yoga. One of them was Maharishi Mahesh Yogi, who popularized Transcendental Meditation. Another one is the prominent Yoga Guru Swami Sivananda who modified five principles of Yoga which are: Shavasana or proper relaxation, Asanas or proper exercise, Pranayama or proper breathing, Proper diet, and Dhyana, or positive thinking and Meditation. Guru Sivananda wrote over 200 books on Yoga and Philosophy and had many disciples who furthered Yoga. Some of them were Swami Satchitananda who introduced chanting and Yoga to Woodstock; Swami Sivananda Radha who explored the connection between psychology and Yoga, and Yogi Bhajan who started teaching Kundalini Yoga in the 70s.